Porpita porpita, commonly known as the blue button, is a marine organism consisting of a colony of hydroids found in tropical waters from California to the tropical Pacific, the Atlantic and Indian oceans It is often mistaken for a jellyfish, but although jellyfish and the blue buttons are part of the same phylum (Cnidaria), the blue button is part of the class Hydrozoa.

"porpita porpita - the blue button jelly - is a neustonic species mostly found in the tropics; that is, it floats near the surface of the water. The circular disc is made of chitin and filled with gas, allowing these jellies to float. The tentacles (zooids) radiating from the disc do all the feeding."